Internal fin for heat-exchanger tubes



July 11, 1950 H. F. BRINEN INTERNAL FIN FOR HEAT-EXCHANGER TUBES FiledNOV. 5, 1947 warm, .%wmdfi Patented July 11, 1950 INTERNAL FIN FORHEA'D-EXCHANGER TUBES Howard F. Brinen, Racine, Wis., assignor to YoungRadiator Company, Racine, Wis., a corporation of Wisconsin ApplicationNovember 5, 1947, Serial No. 784,265

4 Claims. (Cl. 138-38) Increasingly, modern industry is enlargingpower-generating units, particularly for automotive equipment. Thedevelopment of Diesel electric locomotives, Diesel engines for aircraft,and gas-burning turbines exemplifies this trend.

The enlargement of these power-generating units presents a problem ofadequately dispersthe fluid through the tube with the minimum ofturbulence so as to present the least possible resistance to the flow offluid through the tube; and thirdly, the prevention, insofar aspossible, of the accumulation of sludge and the consequent clogging ofthe tube.

It is well known that the use of fins within tubes materially increasesthe heat transference. However, with the internal flns heretoforeprovided, the resulting turbulence in the fluid often is so great thatthe increased resistance to fluid flow completely negatives the gain inheat transference. Moreover, many of the prior fin designs presentobstructions about which sludge tends to accumulate, too often resultingin a clogging if not a closing of the tube.

There is the further problem of providing a fin that can be insertedinto a tube of any material length without causing the fln' to buckleand thereby precluding the use of fins with tubes of any materiallength.

Because of these facts manufacturers of heatexchange equipment of thetubular type have often had to choose between gaining increased heatdispersion, at the sacrifice of free fluid flow, or having a freer fiuidflow with a reduction in heat dispersion.

Flat or elliptical tubes are known to provide a higher degree ofdissipation than circular tubes of the same volumetric capacity.Nevertheless, these foregoing problems are as acute with flat orelliptical tubes as with circular ones.

The main objects of this invention, therefore, are to provide animproved form of internal fins, for heat-exchanger tubes, which secure ahigh degree of heat transference with a minimum resistance to fluid flowthrough the tube, and which occasions the very least likelihood ofsludge accumulation; to provide an improved internal fin of this kindwhich may be inserted into a tube of considerable length withoutbuckling; to provide an improved fin of this kind which when insertedretains itself'in place without the necessity of being bonded to thetube; and to provide an improved internal fin of this kind particularlyadapted for use with fiat or elliptical-shaped tubes.

In the accompanying drawings,

Fig. 1 is a perspective view of a section of a flat or elliptical-shapedtube wherewith is associated an internal fin embodying this invention;

Fig. 2 is a plan view of a fragment of the improved fin removed from thetube;

Fig. 3 is a fragmentary and partly cross-sectional view of a tube of thetype with which this improved fin is particularly suited for use;

Fig. 4 is an enlarged, transverse, cross-sectional view of the tube-finassembly, taken on the line 4-4 of Fig. 1; and

Fig. 5 is an end view of the tube-fin assembly shown in Fig. 1.

A tube 6, for use with which this improved form of internal fin I hasbeen designed, is one of the types of tube quite generally used in theconstruction of heat-exchanger cores for the dispersion of heat from thelubricating oil used in heat-creating, power-generating units. As noted,this is a seamless tube redrawn to the form shown from a cricular tubeproduced by the well-known bench drawing process. The tube could be ofthe seam type wherein a flat piece of thin sheet metal is folded and theabutting edges are bent and interlocked and subsequently bonded to forma fluid-tight joint.

The fin 1, embodying this invention, is of comparatively thinconstruction. In its preferred form, for use within a tube, it is bentalong its longitudinal median to form a central or median ridge 8 and isalso bent longitudinally along the lines 9 and I0 intermediate the ridge8 and the lateral edges H and I 2 so as to form the angularly-disposedborder portions l3 and II. These border portions are preferablyapproximately parallel to the respective portions of the strip whichform the median ridge 8.

Although the ridge 8 is herein shown in the form of a V, some othergeometric form might be effected.

This arrangement of bends to form the median ridge 8 and theangularly-disposed border portions l3 and I4 disposes the intermediateportions l5 and It in a common plane approximately tube 6.

Being made of resilient or spring-like material the fin may be insertedinto the tube so that it will contact the tube 6 along the lateral edgesII and i2 and the apex H (as indicated in Figs. 4 and 5) and will befrictionally held in place by the resiliency oi the fin itself.Therefore, there is no need for bonding the iln to the tube either toretain it in place or to secure appropriate contact of the fin with thetube as above indicated. Moreover, being capable of yielding betweenthese three points of contact with the tube, a fin of considerablelength, in fact several feet, may be inserted into a tube of equallength very easily with no danger whatever of the fin buckling.

Although not imperative by any means, for certain uses the fin will haveapertures i8 punched in the portions l5 and it. Such apertures willpermit the fiuid on either side of the fin to contact the fluid on theopposite side throughout the length of the tube. This will ensure havingthe temperature of the fluid throughout the length of the tubepractically uniform.

Although the use of such apertures may cause a slight amount ofturbulence the other gains in the use of such an internal fin are suchas to make that slight turbulence rather negligible.

Laboratory tests with a fin construction of this kind show an increaseof approximately 22 per cent in heat transference over that obtainedwith the same core without the internal fin. Also these tests show thatthis gain in heat dissipation is obtained with only one third of thepressure drop which results from the use of other types of internalfins.

Other variations and modifications in the details of structure andarrangement of the parts may be resorted to within the spirit andcoverage of the appended claims.

I claim:

1. An internal fin for heat-exchange tubes in the form of an elongatedstrip bent along a longitudinal median to form a ridge and bentlongitudinally intermediate said median ridge and the respective lateraledges so as to angularly dispose the border portions of said stripapproximately parallel to the respective portions of said strip whichform the median ridge whereby said strip upon insertion into a tube isfrictionally retained in place by the three-point contact of the lateraledges of said strip and the apex of the median bend against the walls01' said tube.

2. An internal fin for heat-exchange tubes in the form of an elongatedstrip bent along a longitudinal median to form a ridge and bentlongitudinally intermediate said median ridge and the respective lateraledges so as to angularly dispose the border portions of said stripapproximately parallel to the respective portions of said I strip whichform the median ridge, the bends in said strip being so formed that saidangularlydisposed border portions and the respective sides of saidmedian ridge are disposed in substantially parallel planes and theportions of said strip between said border portions and median ridgeportions are disposed in a plane equidistant between the plane of thelateral edges of said strip and the apex of said median ridge, wherebysaid strip upon insertion into a tube is frlctionally retained in placeby the three-point contact of the lateral edges of said strip and theapex of the median bend against the walls of said tube.

3. An internal fin for heat-exchange tubes in the form of an elongatedstrip bent along a longitudinal median to form a V-shaped ridge and bentlongitudinally intermediate said median ridge and the respective lateraledges so as to angularly dispose the border portions of said stripapproximately parallel to the respective portions of said strip whichform the median ridge whereby said strip upon insertion into a tube isfrictionally retained in place by the three-point contact of the lateraledges of said strip and the apex of the median bend against the walls ofsaid ube.

4. The combination of a flat heat-exchanger tube and an internal fin,said fin being in the form of an elongated strip bent along alongitudinal median so as to form a V-shaped ridge and bentlongitudinally intermediate said median ridge and the respective lateraledges so as to angularly dispose the border portions of said stripapproximately parallel to the respective portions of said strip whichform said median ridge and having the portions of said strip betweensaid border portions and said median ridge disposed intermediate theplane of the lateral edges of said strip and the apex of said V-shapedmedian ridge, whereby the lateral edges of said strip and the apex ofsaid median ridge contact the opposite walls of said tube andfrictionally .hold said fin in said tube.

HOWARD F. BRINEN.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS

